A planned economy is great when you have a few well defined tasks to really worry about. But you can't really become dynamic and resilient like a market economy can. So certain goals, like getting everyone to read or building a spaceship work reasonably well but it simply can't compete with a market economy in the longer run and dies a death of a thousand capitalist cuts eventually.

The Chinese probably have it more right than the Soviets in that they manage a few big things and then let the market more or less self manage to a point so long as the CCP is getting their cut and gives their blessing.